This application relates to optical sensing of surfaces, including optical measurements of surface slopes and other topographical properties of surfaces in flat panels, substrates, and wafers.
Optical interferometry uses optical interference between two at least partially mutually coherent optical beams to obtain useful information carried by the optical interference patterns. For example, optical interferometry can be used for optical sensing and optical interference patterns can be processed to extract information embedded in the wavefront of at least one of the beams as an optical probe beam which interacts with a sample under measurement.